The preparation of cationic starch is a well known commercial process. The basic water-slurry process for the quaternization of starch employing the reaction product of epichlorohydrin and an amine is taught in U.S. Pat. No. 2,876,217. The art also teaches that in such a process an alkali metal salt, e.g. NaCl or Na.sub.2 SO.sub.4 should be used to inhibit gelatinization. The starch is usually slurried in water at a dry weight (d.b.) of from about 10 to about 42%. Reaction times are generally 12-20 hours, the slurry is maintained at a pH of 11-12 and the temperature must be low to prevent gelatinization during the process, generally from room temperature up to about 50.degree. C. The reaction product must then be neutralized and washed to remove salts. According to teachings of U.S. Pat. No. 3,422,087 cationic starch products can be made in the absence of alkali and at temperatures much higher than normal, up to just under 200.degree. C. which is the browning temperature of the polysaccharide.
While the majority of the art recommends using slurries of up to about 40% dry starch solids and a basic catalyst of an alkali or alkaline earth metal oxide or hydroxide, the present inventor has found that a high solids starch slurry of from 42-44% (d.b.) can be effectively used in the method of the prior art, but that when a particular catalyst, consisting of both alkali and alkaline earth metal oxides or hydroxides, is used, a reduction in the viscosity occurs unexpectedly, allowing the use of a higher starch solids content of up to 46% (d.b.) which results in improved conversions and yields of cationic starch.